Compare and Contrast the characters of Professor McGonagall and Severus Snape

Minerva McGonagall and Severus Snape share many similarities. Both attended Hogwarts as children, returning as adults to teach Transfiguration and Potions, respectively. Both are strict disciplinarians who respect school rules, have high expectations for their students, and have earned a great measure of respect from their colleagues, as well as positions of authority at the school, leading the houses of Gryffindor and Slytherin.
Although both exhibit a tendency towards sarcasm and/or similarly barbed commenary, Minerva’s often takes a lighter, more humorous form: alliterative word play. For example, in Harry Potter and the Goblet of Fire, as she prepares students for the Yule Ball, she says, “The house of Godric Gryffindor has commanded the respect of the wizarding world for nearly ten centuries. I will not have you, in one night, besmirching that name by behaving like a babbling, bumbling band of baboons!” Snape’s, often directed at students he deems weak or vulnerable, can be biting and brutal.
Both dress conservatively and seem to favor dark colors: Minerva in long-sleeved, floor-length dresses and robes evocative of the traditional “witch” image, and Snape in attire reminiscent of the Victorian Era.
Loyal to Professor Dumbledore, both McGonagall and Snape shared in his confidence, and were members of the Order of the Phoenix, although where Minerva’s loyalty was unwavering, Snape’s was not.
Another interesting similarity between Minerva and Severus is that both are “half-bloods,” children who had one non-magical parent. In both instances, the "Muggle" parent was the father.
Of the two, Minerva McGonagall is more approachable and likeable. She seems to genuinely like children, enjoy working with them, and actively listens to their concerns. Snape, on the other hand, appears standoffish, mercurial in manner and mood, and tends to make negative snap judgements, particularly where Harry Potter is concerned. While Minerva seems to relish her teaching duties, Snape seems resigned to his role as Potions Master. Though he excels in this area, it is not his favorite subject. Snape’s character, which also is more morally ambiguous than Minerva’s, makes him ideally suited for the role of double agent: loyal to Dumbledore but feigning affiliation with Voldemort and other Death Eaters.